1. Technical Field of the Invention
The present invention relates to telecommunications equipment and components and, more particularly, to a system and method for providing the capability to withstand high voltages between pins of a high-density compliant pin connector used in network equipment.
2. Description of Related Art
A common requirement of telecommunications equipment is resistance to foreign voltages such as lightning and power-cross, particularly when the equipment has connections to outside plant cables. With the use of high-density press-fit compliant pin connectors such as 2 mm Hard Metric or Futurebus styles, it is difficult to achieve sufficient space between pins and connector pads to prevent arcing and/or failure under severe lightning conditions.
Two solutions exist for increasing the high voltage resistance capability between pins and connector pads to prevent arcing. In one technique, the printed circuit board (PCB) or backplane that receives a high-density compliant pin connector is provided with a complete conformal coating to prevent arcing. While effective, the conformal coating method is beset with several deficiencies and drawbacks. First, conformal coating is expensive, thereby adding to the component""s cost of manufacture. Also, reworking conformally coated components is inefficient because the coating is difficult to remove once applied. Consequently, manufacturability of conformally coated components is negatively impacted. Moreover, most customers do not accept conformally coated products.
With respect to the other solution for reducing inter-pin or inter-pad arcing, one or several pins interspersed between high voltage pins of a high-density compliant pin connector are left unconnected so as to increase the physical distance, and thereby the electrical path, between the high voltage pins. Although this technique is known to diminish the risk of inter-pin arcing, those skilled in the art should readily appreciate that several disadvantages remain in the practice of the solution. First, leaving unconnected pins in a connector to give physical separation wastes pins (which adversely affects the pin budget in an application) and can greatly increase connector size and cost. Furthermore, the option of leaving unconnected pins may not be available in existing connector designs where changes to connector pin usage are not permitted because of, for example, the requirement of backward compatibility with the PCB/backplane receptacles.
Accordingly, the present invention is directed to a system and method for providing high voltage resistance capability in a receptacle for accepting a high-density compliant pin connector wherein inter-pin arcing is advantageously reduced. A plurality of high-density compliant pin through-holes are formed in a printed circuit board (PCB) for receiving the pins of the high-density compliant pin connector. The through-holes are plated using an electrically conductive material, whereby conductive pads are formed around the plated through-holes on at least one side of the PCB. Thereafter, the conductive pads around the plated through-holes on the PCB are removed by controlled depth back-drilling. Accordingly, the receptacle""s PCB is provided with a plurality of back-drilled portions around the through-holes formed therein so as to increase the inter-pad clearance of the through-holes for withstanding foreign voltages.
In a presently preferred exemplary embodiment, the through-hole plating is comprised of two metallic layers: an inner copper (Cu) layer and an outer tin/tin-lead (Sn/SnPb) layer. The inner copper layer is provided with a plurality of internal pad structures interior to the PCB. Where external conductive pads comprised of metals or metallic compounds are formed on both sides of the PCB, the technique of controlled depth back-drilling is preferably used to remove such metallic pads on each side of the PCB.